Monday, April 20, 2015

As a child of the ’80s, I saw Short Circuit more times than I can count. To this day whenever I take something apart I hear the terrified Number 5 yelling, "Disassemble?! No!!" as he realizes what it would mean for him. But I still take things apart, because it is fun.

There have been many things I've collected (okay, maybe call it hoarded) over the years for use in my classroom. Some I have specific and immediate uses for .... some not so much. I still have part of the framing from a holiday light lawn sculpture of a snowman that I just know will be perfect for something, someday.

I finally got the time this year to disassemble an old toaster, hair dryer and space heater. I reference these appliances when I teach electricity as a practical example of the conversion of electric energy to thermal energy. By the time we get to that, students have often had personal experience with that conversion when they leave their circuits on too long and touch hot resistors.

Even though we've talked about the dissipation of heat from electrical circuits I don't think my students believed me until they saw all those coils of wire. It was a simple thing to take them apart (they weren't working anyway) but many of my students were just in awe of seeing the inside of something. Little do they know they get to do it next week.

Now that our current electricity unit has come and gone we have moved on to electromagnetism. I have my students make a speaker out of paper using a paper template I made (pdf or google doc), a doughnut magnet and a coil of magnetic wire. Its a simple build based on Modesto Tamez's activity from the Exploratorium, but the students love it every year. It can be expanded by asking students to improve the design, increase the volume or efficiency. I've also seen a headphone project follow this for which students have to make their own working headphones based on this speaker design. (NGSS Science & Engineering Practice right there!)

This year I'm adding a "Dissecting Headphones" lab to my unit. Thanks to RAFT I scored a gross of cheap ear bud headphones several years ago that I've been holding on to (hoarding again). Each pair of students will get a set of headphones so that they each get to dissect one ear bud. The instructions go step by step for these particular headphones and lead students all the way to the small magnet and coil. I've done it with high school aged students before and despite building the paper speaker only a few minutes before, they are shocked—shocked—that their ear buds work the same way. They use classroom scissors and a straight pin; they can use wire cutters too, but they are not required.

Suddenly they all start making connections. "This is how a microphone works, too!" and "That's why my headphones attract paperclips!" are heard all over the room. And it's magical.

The lab my students will do this week includes both the "Make A Speaker" and "Dissecting Headphones" labs in one file available as a pdf or google doc.

If you're hip enough to have tuned into this blog, you've probably seen the viral video of the cinder-block smash demo gone wrong. I'm not linking to it directly, because it's not any fun to watch. Of course, in this modern era, you can find versions of this incident from multiple angles.

I have mixed feelings about this demo and have never done it, myself. But I think Greg Schwanbeck makes a powerful argument against the knee-jerk reaction that will likely follow.

Disclaimer

The views expressed in this blog are those of the post authors and commenters. They are not necessarily those of The San Juan Unified School District, The California Department of Education, Pearson Education (or any of its imprints).